Acute GI bleeding is a common indication for therapeutic endoscopy. Several methods of endoscopic hemostasis are available including thermal therapy (heater probes, electrocautery, argon plasma coagulation, and lasers), injection therapy, and mechanical devices (band ligation, clips, and detachable loops). Although several devices and methods for treating gastrointestinal bleeding exist, advances in the development of hemostatic devices are still needed for situations such as massive bleeding, bleeding from malignant ulcerated tumors, and bleeding arising from vessels located deep within the GI wall. High-intensity focused ultrasound (HIFU) represents a new method that may have applications in treating gastrointestinal bleeding. HIFU applied to tissue can result in a rapid rise in temperature approaching 100xC in 1 second within the focus of the HIFU transducer without damaging the intervening tissue. This thermal effect is due to absorption of acoustic energy by tissue in a small focal volume due to focusing of the ultrasound beam similar to a magnifying glass focusing sunlight. HIFU has been demonstrated to achieve hemostasis in punctured arteries and veins in animals models thought to be due to thermal coagulation. We have performed initial hemostasis studies in lacerated rabbit auricular veins and arteries that suggest HIFU may be effective in the treatment of acute GI bleeding. The development of a probe suitable for the endoscopic delivery of HIFU followed by in vivo studies in large animals with GI bleeding is proposed. It is anticipated that this work will help to gain a better understanding of the mechanisms of HIFU and its potential role for other GI applications such as tumor therapy.